Pyrotechnic circuit breaker

ABSTRACT

A pyrotechnic circuit breaker includes a housing with at least one cutting chamber, at least one electrical conductor, at least one punch designed to section the at least one electrical conductor, at least one pyrotechnical actuator, and an insert moulded on the at least one electrical conductor. The housing includes a first housing part and a second housing part with at least one sealing means between the insert and one of the first housing part and/or of the second housing part in order to ensure a seal of this at least one cutting chamber.

The present invention relates in a general manner to a circuit breakercomprising a pyrotechnical actuator intended to be mounted on anautomobile, and in particular on an electrical vehicle.

It is necessary in such electrical vehicles to provide the ability tobreak the electrical lines connecting the energy storage devices(batteries, super-condensers, . . . ) to the rest of the vehicle inorder to make the latter safe if an accident occurs, for example. Due tothe powers involved and the characteristics of the electrical circuits,electrical arcs will occur during the breaking and call into questionthe breaking of the circuit and its integrity if these arcs are notcontrolled. Circuit breakers are known in the prior art such as the onedisclosed in the document EP0359467A2 and which propose specificarrangements for extinguishing electrical arcs. On the other hand, thissystem has in particular the disadvantage of being bulky if it is usedto break electrical circuits with elevated voltages and/or currents.

A goal of the present invention is to respond to the disadvantages ofthe above-cited documents of the prior art and in particular to at firstpropose a circuit breaker which is compact and which brings about arapid break even if an electrical arc is formed.

To this end a first aspect of the invention relates to a circuit breakercomprising:

-   at least one electrical conductor designed to be connected to an    electrical circuit,-   a housing,-   a matrix,-   a punch designed to be movable relative to the housing in order to    pass from a first position to a second position,-   a pyrotechnical actuator designed to make this punch pass from the    first position to the second position when it is ignited,-   which punch and matrix are arranged to form a punch-matrix unit    designed to be able when the punch passes from the first position to    the second position to:

break the at least one electrical conductor into at least two distinctparts, and

bring about the establishing, between the punch and the matrix, of atleast one electrical arc between the at least two distinct parts whenthe circuit breaker is connected to a live electrical circuit,characterised in that:

-   the punch-matrix unit, when the punch is in the second position, is    designed to allow at least one passage between the at least two    distinct parts, which at least one passage is designed to guide said    at least one electrical arc between the distinct parts, and that The    punch-matrix unit comprises at least one material designed to be    withdrawn by ablation by said at least one electrical arc in order    to generate gas suitable for increasing a voltage of said at least    one electrical arc.

The circuit breaker according to the present invention allows theformation of electrical arcs created when the punch breaks theelectrical current into two distinct parts to be controlled. In fact,when the punch is in the second position, a passage is formed by thepunch-matrix unit so that the electrical arc or arcs are guided throughthe passage, which guarantees their localisation and limits the risk ofdamaging the rest of the circuit breaker. Furthermore, the efficiencyand the rapidity of the circuit breaker are improved by the materialdesigned to be withdrawn by ablation which allows the voltage of theelectrical arc to be increased once the pyrotechnical actuator hasfunctioned, that is, the circuit breaker will be efficient even for anelevated voltage at its terminals without increasing the separationsbetween the distinct parts, which improves the compactness. In fact, thematerial designed to be withdrawn by ablation is sublimated under theaction of the flow of intense heat of the electrical arc, which modifiesthe composition of the plasma of the electrical arc and its conductivityand allows the voltage of an electrical arc to be increased. Suchelectrical arcs can be created when the circuit breaker is connected toa live electrical circuit with voltages ranging from 0 V to 600 V andcurrents ranging from 0 A to 5,000 A on inductive charges ranging up to2,500 μH (micro-Henries) for an intensity lower than 500 A and up to 150μH for an intensity of 5,000 A. The circuit breaker of the inventionallows the current to be broken in a reliable manner in less than 10 msand even less than 5 ms in a definitive manner because the circuitbreaker, which comprises a pyrotechnical actuator, can only be usedonce.

The passage can advantageously be formed between the punch and thematrix or in one of these pieces.

Either the punch or the matrix is advantageously at least partiallyrealized with the material designed to be withdrawn by ablation.

The material designed to be withdrawn by ablation is advantageously POM(polyoxymethylene or polyformaldehyde)). According to thisimplementation the material to be withdrawn by ablation will allow thecreation, during the ablation, of a gaseous mixture which increases thevoltage of the electrical arc because the POM presents a ratio of thenumber of carbon atoms to the number of oxygen atoms which is very low,close to 1. It is also possible to envision using ethylenepolyterephthalate (PET), methyl polymethacrylate (PMMA), butylenepolyterephthalate (PBT), polyether sulfone (PESU) or even polyamide 6-6(PA6.6).

Said at least one passage is advantageously at least partially limitedby the material which can be withdrawn by ablation. The presentimplementation increases the efficiency of the circuit breaker becausethe material to be withdrawn by ablation by the electrical arc islocated in its immediate vicinity, which guarantees a rapid increasingof the voltage of the electrical arc due to the ablation of thematerial.

Said at least one passage is a groove advantageously formed in the punchor and/or the matrix. It is possible to envisage a groove whosedimensions would be the following: width ranging from 0.1 to 1millimetre and depth ranging from 0.1 to 1 millimetre. Such a groove canbe directly obtained by moulding if the dimensions are compatible withthis technology and the injected material, or by re-machining.

When the punch is in the second position the punch and the matrix areadvantageously arranged with a tight adjustment with the exception ofsaid at least one passage. According to the present implementation thepunch and the matrix have a tight adjustment in order to guarantee theirreversibility of the movement of the punch, which prevents on the onehand any movement to the rear. On the other hand, this tight adjustmentbrings about a good tightness which forms a natural barrier against thepassage of the electrical arc when somewhere else than in the passage.Consequently, the electrical arc is forced to pass through the passage,which remains free and at the level of which the punch and the matrixare not in a condition of a tight adjustment (since there is a play). Itis possible to envisage providing a negative play from 0 to 0.3millimetres between the punch and the matrix.

Advantageously:

-   each of these at least two distinct parts has a cut end separated    from each other when the punch is in the second position.-   the at least one passage is designed over the shortest path between    the cut ends. Once the passage is formed over the shortest path    between the cut ends, the path of the electrical arc will be    favoured there since it is the path which requires the least energy.

The circuit breaker advantageously comprises an insert which comprises aguiding part for the punch and a reinforcement part for the matrix. Theinsert according to the present implementation is a single continuousand mono-block piece which combines the function of guiding the punchand the function of reinforcing the matrix. The assembly can be made bymoulding it on the electrical conductor, which minimizes the risk of anoffset between the punch (guided by the guiding part of the insert) andthe matrix (therefore reinforced positioned by the reinforcement part).

The insert is advantageously made of polyamide 6-6 (PA6.6) charged with30% of glass fibres.

The insert advantageously comprises a face designed to enter into amechanical stop block between the punch, thus defining the secondposition.

The matrix is advantageously designed to be deformable in an elasticmanner in such a manner as to guarantee a surface contact with theexception of said at least one passage with the punch when the punch isin the second position. The path of the electrical arc becomes all themore difficult when in the passage with a surface contact between thepunch in the matrix.

The matrix advantageously comprises a recess designed between it and thereinforcement part. This recess allows the matrix to move and/or bedeformed under the action of the punch in order to align itself with thelatter and ensure a good tightness between the punch and the matrix. Itis possible to envisage that the recess is comprised between 0 and 2millimetres, more particularly between 0 and 1 millimetre and veryadvantageously between 0 and 0.5 millimetres.

The matrix advantageously comprises a connection point with thereinforcement part which separates two recesses between the matrix andthe reinforcement part. This implementation allows a pivoting of amatrix wall around the connection point and not a crushing. Thisconnection point can be placed facing the passage in such as manner asto control the section of the passage available for establishing theelectrical arc.

The punch in the second position and the housing advantageously form atleast one break chamber and this at least one break chamber comprises avent hole to the outside of the circuit breaker and with a lid, designedto break beyond a predetermined pressure difference between said atleast one break chamber and the outside of the circuit breaker. Thepresent implementation proposes a safety valve in the break chambercalibrated to open at a given pressure. This allows an excess pressureto be evacuated without calling into question the integrity of thedevice if it functions beyond nominal conditions, while guaranteeing atight system under nominal conditions.

The punch advantageously comprises two break edges in such a manner asto break the at least one electrical conductor into three distinctparts. This implementation forces the creation of two electrical arcsthe series with one another which increases the breaking characteristicsof the circuit breaker.

The circuit breaker advantageously comprises an insert which comprises aguiding part for the punch and a reinforcement part for the matrix. Theinsert according to the present implementation is a single continuousand mono-block piece which combines the function of guiding the punchand the function of reinforcing the matrix. The assembly can be made bymoulding it on the electrical conductor, which minimizes the risk of anoffset between the punch (guided by the guiding part of the insert) andthe matrix (therefore reinforced positioned by the reinforcement part).

The matrix advantageously comprises a counterform designed between thetwo breaking the edges in such a manner as to define two breakingchambers when the punch is in the second position

The punch is advantageously designed to be mobile along a predeterminedaxis of translation and the matrix is designed in a symmetrical mannerrelative to the axis of translation of the punch. The cutting strainsare symmetrically distributed, which limits the risk of jamming.

The punch advantageously comprises at least one beveled cutting edge inorder to cut the at least one electrical conductor progressively duringits passage from the first to the second position. The cutting stress inthis implementation is lower than the one required by a straight cuttingof the electrical conductor in which each section is cut at a singletime. This reduces the pressures to be implemented and also the bulk ofthe circuit breaker with this progressive, beveled cut.

The beveled cut edge advantageously has an angle comprised between 90°(terminal excluded) and 75° relative to the direction of the movement ofthe punch.

The punch advantageously comprises a cutting edge in the shape of a “V”with the point of the “V” positioned in the middle of the cutting edgeso that the point of the “V” finishes cutting the electrical conductor.This allows the establishing of the electrical arc in the middle of thedevice and a better balance of the forces in play. in this embodimentthe passage is arranged in the extension or facing the point of the “V”.

-   -   A second aspect of the invention relates to a device for        distributing current comprising at least one circuit breaker        according to the first aspect of the invention.    -   A third aspect of the invention relates to an automobile        comprising at least one circuit breaker according to the first        aspect of the invention.    -   The automobile advantageously comprises means for storing        electrical energy and an electrical propulsion device connected        to the means for storing electrical energy by said at least one        circuit breaker.

Another goal of the invention is to propose a pyrotechnical circuitbreaker with a break chamber which is easy to manufacture and whichbrings about a seal during the operation in order to guarantee theconfining of the gases heated by the electrical arc or arcs and toguarantee the non-polluting of the interior of the device by the gases,the humidity or dust coming from the outside of the device before itsoperation as an indication of protection IP67 according to theinternational norm CEI 60529en.

To this end a fourth aspect of the invention relates to a pyrotechnicalcircuit breaker comprising:

-   A housing with at least one break chamber,-   at least one electrical conductor to be sectioned traversing at    least a part of the housing of said at least one break chamber,-   at least one punch arranged in the housing facing said at least one    break chamber and which can move between a first position and a    second position and which punch is designed to section said at least    one electrical conductor during its passage from the first to the    second position,-   at least one pyrotechnical actuator designed to make said punch pass    from the first position to the second position when it is activated,-   an insert moulded on said at least one electrical conductor,    characterised in that the housing comprises a first housing part and    a second housing part with at least one sealing means between the    insert and one of the first housing part and/or of the second    housing part in order to ensure a seal of this at least one break    chamber.

The circuit breaker according to the above implementation ensures a goodseal of said at least one break chamber with the sealing means. However,it remains easy to manufacture because the insert avoids having toprovide sealing interfaces on the electrical conductor itself andbringing them back onto the insert. Therefore, these bearing surfacescan be continuous without slipping in order to facilitate theimplantation of the sealing means such as a toric joint for example. Inother words, the seal is realised between only two pieces facing eachother at each time: between the first housing part and the insert on theone hand and between the second housing part and the insert on the otherhand.

The at least one electrical conductor is advantageously arranged betweensaid at least one break chamber and the punch when the latter is in thefirst position.

The first housing part and the second housing part are advantageouslyeach in contact with the insert. This allows a good passage of thestrains between the different elements of the device and allows a goodresistance of the assemblage to be ensured.

The insert is advantageously arranged between the first housing part andthe second housing part and the circuit breaker comprises first sealingmeans between the insert and the first housing part and second sealingmeans between the insert and the second housing part.

The insert advantageously surrounds said at least one break chamber,This implementation guarantees that the seal on the insert will becontinuous. It is possible to envisage that the insert surrounds orcircumscribed said at least one break chamber on both sides of theelectrical conductor. In this implementation said at least one breakchamber can be defined in part by the insert and there is no need toprovide a joint between the electrical conductor and the housing.

The first housing part and the second housing part are advantageouslyeach arranged to be assembled on the insert along one direction ofmovement of the punch. It is quite possible to envision a male-femaleassemblage with the housing parts that slide on the insert during theirassembly in order to come into the final assembled position. Therefore,the guiding of the punch is improved because the first part and thesecond part are positioned relative to the same piece, the insert.

The punch advantageously comprises a sealing zone in order to ensure aseal between the punch and the insert and/or the housing. This seal canbe provided between a combustion chamber of the circuit breaker and saidat least one brake chamber in order to avoid any influence of thecombustion gases of the pyrotechnical actuator on the electrical arc orarcs.

The insert advantageously surrounds said at least one electricalconductor on at least two distinct zones. This implementation allows itto be guaranteed that no sealing function will be made on the electricalconductor itself. It is the moulding on that makes this seal around theelectrical conductor. In other words, no seal needs to be providedbetween the conductor and the first and the second housing parts.

The punch in the second position is advantageously arranged between saidat least two distinct zones.

The insert advantageously comprises at least one moulded-on partarranged in a retention means of said at least one electrical conductor.The retention means can have the shape of one or several holes, cavitiesor cuts. This implementation allows the increasing of the unity of theinsert with the electrical conductor and to therefore improve the sealbetween the two pieces.

Said at least one sealing means advantageously comprises a joint. Atoric joint can be envisaged.

The circuit breaker advantageously comprises two joints and the insertcomprises two joint bearing surfaces, each facing a joint bearingsurface of the first housing part and a joint bearing surface of thesecond housing part.

It is possible to provide one or more toric joints in order to realisethe sealing means. In particular, it is possible to provide toric jointswith a diameter comprised between 2 mm and 3 mm with a compressionranging from 0.5 to 0.8 mm. More precisely, it is possible to provide atoric joint with a diameter of 2.55 mm±0.15 mm with a compression of 0.7mm±0.15 mm.

The circuit breaker advantageously comprises at least one moulded-onsealing lip.

The first housing part and the second housing part are advantageouslywelded. Each housing part can be welded on the insert.

Other features and advantages of the present invention will appear moreclearly from a reading of the detailed following embodiment of theinvention given in a non-limiting manner by way of example andillustrated by the attached drawings, in which:

FIG. 1 shows a sectional view in perspective of a pyrotechnical circuitbreaker according to the invention before operation;

FIG. 2 shows a detail from the section of FIG. 1 after the functioningof the circuit breaker;

FIG. 3 shows a partial section of the circuit breaker along axis III-IIIFIG. 2;

FIG. 4 is a perspective view of detail IV from FIG. 1.

FIG. 1 shows a perspective view of a circuit breaker according to theinvention in section. A housing 1 is partially traversed by anelectrical conductor 2 and the ends of the latter form two connectionterminals for the circuit breaker. The circuit breaker comprises a punch4 and a matrix 3 which are arranged before the operation of the circuitbreaker on both sides of the conductor 2 as shown in FIG. 1.

The punch 4 comprises on its upper part facing the matrix 3 a groovelimited by two cutting edges 8 and 8′ and a passage 6 which is avertical groove connecting the cutting edge 8 to the bottom of thegroove of the punch 4. Another passage, which is not visible, connectsthe cutting edge 8′ to the bottom of the groove of the punch 4. Theutility of the passage 6 will be explained in particular in theparagraphs relating to FIG. 3.

The punch 4 is shown here in a first position in which the electricalconductor 2 is integrated. In order to cut it the circuit breakercomprises a pyrotechnical actuator 5 (visible only in FIG. 2) which isdesigned to make the punch 4 pass into a second position such as isshown in FIG. 2.

For example, the electrical conductor 2 can have a section of 2 mm×16mm, a residual thickness facing the punch 4 of 1.2 mm and the groove ofthe punch 4 has a length of 5 mm±1 mm.

FIG. 2 therefore shows the circuit breaker of FIG. 1 after functioning,that is, with the electrical conductor 2 separated into three distinctparts 21, 22 and 23. In order to obtain this result the pyrotechnicalactuator 5 (comprising an electro-pyrotechnical igniter, for example)located under the punch 4 was ignited and generated gases in such amanner as to pressurise a combustion chamber 41.

Under the effect of the gases and of their pressure in the combustionchamber 41 the punch 4 passed into a second position during a movementof translation during which the conductor 2 was therefore separated intothree distinct parts 21, 22 and 23. As is shown in FIG. 1 or 3, thecutting edges 8 and 8′ are not rectilinear but in a V in such as manneras to progressively cut the electrical conductor 2 with cutting strainsless than those necessary for a simultaneous cutting of the entiresection of the electrical conductor 2. In fact, with these cutting edges8 and 8′ which are beveled or not beveled perpendicular to the directionof movement of the punch 4, the cut of the electrical conductor 2 isprogressive.

It can be noted that the punch 4 comprises a groove in which a toricjoint is mounted in order to guarantee a good seal of the combustionchamber 41. This therefore achieves a cutting stress of the punch 4which is as elevated as possible and the gases of the pyrotechnicalactuator 5 cannot enter into the cutting chambers 7 and 7′, which limitsthe possible pollution of the plasma of the electrical arc by the gasesof the pyrotechnical actuator 5.

With the punch 4 in the second position, the groove of the punch 4 isengaged in the matrix 3, and two distinct cutting chambers 7 and 7′ havebeen formed. The part 21 of the electrical conductor 2 is thereforephysically separated from the part 22 of the electrical conductor 2 bythe punch 4, which limits the possibility of creating an electrical arcdirectly between the parts 21 and 22 and even more so when in the secondposition the punch 4 is tightly mounted on the matrix 3.

This type adjustment achieves several results. On the one hand themaintaining of the punch 4 in the second position is guaranteed by thistight mounting in such a manner that the separation of the cuttingchambers 7 and 7′ is guaranteed in time. It should be noted that thecircuit breaker comprises a vent hole 9 with a lid (visible in FIG. 1)for each cutting chamber 7 and 7′ in such a manner that it only openswhen the pressure in the cutting chamber 7 or 7′ concerned exceeds athreshold value.

On the other hand, the tight adjustment allows the bringing about orcreating an elastic and/or plastic deformation of the punch and/or ofthe matrix 3 which will therefore be in surface contact with one anotherwith a good seal at the end between the cutting chambers 7 and 7′. Thisseal allows the avoidance of the creation of electrical arcs between thecutting chambers 7 and 7′ and the distinct parts 21, 22. However, ascited above, a passage 6 connects the cutting edges 8 and 8′ of thepunch 4 at the bottom of the groove of the punch 4, as shown in FIG. 3,and this passage 6 allows the electrical arcs created during the cuttingof the electrical conductor 2 to be located with certainty. A first arccan therefore be formed between the distinct part 21 and the distinctpart 23 and a second one can be formed between the distinct part 23 andthe distinct part 22.

The matrix can be deformed from 0 to 2 millimetres, preferably from 0 to1 millimetre and even more preferably from 0 to 0.5 millimetres. To thisend a recess is formed between the matrix 3 and an insert 31 whichauthorises such movements and/or deformations.

As shown in FIG. 4, which is a perspective view of a part of the insert31 of detail IV of FIG. 1, the insert 31 comprises a recess along theinterface with the matrix 3. This recess is delimited by a part 31 ofthe insert 31. The part 31 a forms a stop for the matrix 3, preventingit from re-tightening on itself over the length of the conductor 2 atthe moment of the cutting of the conductor 2 while leaving thepossibility for the matrix 3 to be deformed above the part 31 a. Thisfreedom of deformation allows a good surface contact to be guaranteedexcept for passage 6 between the punch 4 in the matrix 3 in the secondposition.

For example, the height of the parts 31 a can be comprised between 0.5mm and 5 mm and the recess can have a reduction of length of 0.5 mm to 1mm.

The insert 31 can be made of polyamide 6.6 and has the main function ofreinforcing the matrix 3. Therefore, as is shown, the insert 31 forms abore in which the punch 4 slides, which offers a direct positioningbetween the punch 4 in the matrix 3 since they are the same piece.

As FIG. 1 and FIG. 2 show, the housing 1 is formed by two distinct partswith a first housing part and a second housing part on each side of themolded-on insert 31 which comprises two male parts which allow thereception of the upper housing and of the lower housing during theassembly.

As was seen above, the cutting chambers 7 and 7′ and the punch 4 aredefined in such a manner as to force the establishment of arcs in thepassages, allowing only the latter as a communication path between thecutting chambers 7 and 7′. The moulded-on insert 31 as well as at leastone toric joint 32 between the first housing part and the moulded-oninsert 31 allow the confining of the gases naturally present in thecutting chambers 7 and 7′ in the latter even if these confined gases arereheated by the electrical arcs.

Moreover, since the moulded-on insert 31 completely surrounds each ofthe distinct parts 21 and 22 as well as the cutting chambers 7 and 7′the sealing interface is then particularly easy to design with, as here,the toric joint 32 mounted in an inclined part of the first housing partand compressed by the moulded-on insert 31. Only two pieces are incontact with the toric joint 32, which offers a simple mounting anddesigning.

For example, it can be provided that the toric joint 32 has a diameterof 2.55 mm and is compressed by 0.7 mm.

Therefore, the gas leaks (and possibly that of the electrical arcs) areprevented up to pressures at least equal to 2 MPa, preferably 3 MPa, andeven more preferably 5 MPa in the cutting chambers 7 and 7′.

Moreover, the moulded-on insert 31 coupled by sealing allows theobtaining of a seal with the level IP67 as defined in the standardsDIN40050, CEI 60529 or BS 5490. This allows the avoiding of anyintrusion of a body into the circuit breaker which could alter itsfunctioning. This allows the circuit breaker to be able to be positionedat a greater number of locations in the vehicle.

It can also be possible to provide a second toric joint between thesecond housing part and the moulded-on insert 31 as can be seen in FIGS.1 and 2.

Therefore, the seal of the device is always ensured at the interfacebetween two pieces and never at the interface of three pieces as wouldbe the case if the device was not provided with the moulded-on insert31. In other words, this aspect of the invention proposes an insertmoulded on the electrical conductor in order to have a seal ensuredsolely between the insert and one of the housing parts at a time.

FIG. 3 shows a partial section of the circuit breaker along axis III-IIIin FIG. 2 without the matrix 3 (not shown for reasons of clarity). Thepart 21 of the electrical conductor 2 was moved upward by the cuttingedge 8 and folded in a V on account of the V shape of the cutting edge 8of the punch 4. The part 23 of the electrical conductor 2 remained atthe bottom of the groove of the punch 4 and FIG. 3 shows the passage 6which connects the cutting edge 8 to the bottom of the groove of thepunch 4.

Because of the electrical characteristics of the circuit for which thecircuit breaker is provided (with voltages ranging from 0 V to 600 V andcurrents ranging from 0 A to 5,000 A on inductive charges ranging up to2,500 pH (micro-Henries) for an intensity lower than 500 A and up to 150pH for an intensity of 5,000 A an electrical arc will be formed when thepunch 4 passes from the first position to the second position and cutsthe electrical conductor 2. This electrical arc, when the punch 4 is inthe second position, will naturally travel through the passage 6 for thereasons given below.

At first, the punch 4 and the matrix 3 are in a tight adjustment andonly the passage 6 is a free passage between the cutting chamber 7 andthe bottom of the groove of the punch 4. Finally, the passage 6 isarranged at the shortest passage between the part 21 of the electricalconductor 2 and the part 23 of the electrical conductor 2. In fact, thepassage 6 empties in its upper part at the level of the lower part ofthe V of the part 21 of the electrical conductor 2. Because of thecutting into three distinct parts, two electrical parts are created inseries, which increases the total voltage of the arcs and therefore thevoltage on the terminals of the circuit breaker, which allows the valueof the current in the electrical circuit to be canceled.

Due to the passage 6 the electrical arc is localised and must passthrough the passage 6. The invention proposes in addition to increasethe voltage of the electrical arc when the latter has been formed. Tothis end a material designed to be withdrawn by ablation is supplied inthe vicinity of the passage 6 since the electrical arc will be presentthere. This material designed to be withdrawn (or eroded) by ablationwill be sublimated and/or vaporised by the strong flow of heat imposedby the electrical arc, which modifies the composition of the plasma ofthe electrical arc and therefore its conductivity. By selecting thematerial to be withdrawn by ablation among the plastics, the voltage onthe terminals of the arc is increased and good results are obtained withPOM called polyoxymethylene (or polyformaldehyde) because this materialhas a low ratio of carbon atoms relative to the oxygen atoms.

Finally, it can be noted that the size of the passage 6 can conditionthe quantity of material withdrawn by ablation and that the lower thesize of the groove forming the passage 6 is, the greater the erosionwill be. Good results are obtained with a groove with a width rangingfrom 0.1 to 1 millimetre and a depth ranging from 0.1 to 1 millimetre.

It is understood that various modifications and/or improvements obviousto a person skilled in the art can be added to the different embodimentsof the invention described in the present description without leavingthe scope of the invention defined by the attached claims. cm 1-27.(canceled)

28. A pyrotechnic circuit breaker comprising: a housing with at leastone cutting chamber; at least one electrical conductor to be sectionedtraversing at least a part of the housing at a level of the at least onecutting chamber; at least one punch arranged in the housing facing theat least one cutting chamber and moveable between a first position and asecond position, the at least one punch designed to section the at leastone electrical conductor during passage from the first to the secondposition; at least one pyrotechnical actuator for making the punch passfrom the first position to the second position when activated; an insertmoulded on the at least one electrical conductor; wherein the housingincludes a first housing part and a second housing part with at leastone sealing means between the insert and one of the first housing partand/or of the second housing part to ensure a seal of the at least onecutting chamber.
 29. The circuit breaker according to claim 28, whereinthe insert is arranged between the first housing part and the secondhousing part and includes first sealing means between the insert and thefirst housing part and second sealing mechanism between the insert andthe second housing part.
 30. The circuit breaker according to claim 28,wherein the insert surrounds the at least one cutting chamber.
 31. Thecircuit breaker according to claim 28, wherein the first housing partand the second housing part are each arranged to be assembled on theinsert along one direction of movement of the punch.
 32. The circuitbreaker according to claim 28, wherein the punch includes a sealing zonein order to ensure a seal between the punch and the insert and/or thehousing.
 33. The circuit breaker according to claim 28, wherein theinsert surrounds the at least one electrical conductor on at least twodistinct zones.
 34. The circuit breaker according to claim 28, whereinthe punch in the second position is arranged between the at least twodistinct zones.
 35. The circuit breaker according to claim 28, whereinthe insert includes at least one moulded-on part arranged in a retentionmeans of the at least one electrical conductor.
 36. The circuit breakeraccording to claim 28, further comprising two joints, the insertincludes two joint bearing surfaces, each facing a joint bearing surfaceof the first housing part and a joint bearing surface of the secondhousing part.
 37. The circuit breaker according to claim 28, furthercomprising at least one moulded-on sealing lip.
 38. The circuit breakeraccording to claim 28, wherein the first housing part and the secondhousing part are welded.
 39. The circuit breaker according to claim 28,in combination with an automobile.